gun pressure question

S

Steves69LS3

hi all, is it normal for me to up the pressure on my gun to 90 psi for it to spray good?
i have a guage at the gun and when i went to spray my epoxy at the recommended 35psi, the spray seemed weak and mottled even sitting there adjusting fluid and fan. but when i upped the pressure the better it atomized and spray really good. i am using an astro pneumatic hvlp 1.4 tip. i clean my guns really well after each use

thanks

Steven
 
Are you checking the pressure with your trigger pulled? If so, 90 is really high. I would start around 35 or so with the trigger in.

Is astro pneumatic the same as Asturomec / Walmec the Italian guns? If so, I have one. If I can remember, I think I keep it around 30.
 
no, it is without the trigger pulled. is that how it is done? the operating pressure is the reading when the trigger is pulled? if so then my question has been answered.

thank you

Steven
 
Yes, trigger pulled full open and then set your air pressure. Set the wall regulator up to 90 or so and then set your "at the gun" pressure.
I have found that my Iwata needs to be spraying paint or it will drop 2-3 psi from what I set it at dry.
You should be doing spray outs on masking paper to be sure your pattern is set correctly before painting anything. Some guys get to the point where they can set the gun without it but I am not there yet. Just seems to be good insurance to see a correct spray pattern on paper before turning the gun toward the car.
 
yes i do a sprayout before i paint. but i guess i never thought that there was something wrong about how the gun sprayed because i never really sprayed a big area.

in the top right of the pic you can see my sprayout paper :)

2505699410080454139S600x600Q85.jpg
[/URL][/IMG]
 
My Iwata drops a couple psi between air and fluid too. It doesn't make much difference with my other guns for some reason.

Maybe someone can tell me what is wrong with my setup. I have an 80 gallon IR compresssor. If it is pumped up to 130, I can spray my whole car body, and it might drop to 90 and kick on at the end. By this time, the pressure at my gun has dropped from 27.5 to around 24-25. The reg on the wall is set at 100. I don't think my compressor is adjustable as far as on and off pressure. Any thoughts?
 
Nothing wrong with the compressor. You most likely have a piss poor regulator that isn't holding its set point very well. A good regulator will give a constant output pressure without influence from the input pressure.

You should be able to set the regulator @ 25 psi with 90 psi in the tank ( just leave the compressor off for the test) with the trigger pulled full open, spraying material. Now turn on the compressor and let it pump up to 130. You should still be able to pull the trigger full open and have the same 25 psi at the gun without any adjustments. There may be a 1/2 # change but more than that is a sign of a poor regulator.

Try setting the wall regulator at 90 since you will have tank pressure drop to that pressur before turn on. 90 at the tank is more than adequate pressure, 3/8 id is adquate for hose, hi flow fittings are another must.

hope this helps
 
Sounds to me like you have an airflow problem also. The bigger the line from the tank like 1/2" or 3/4" through a hi flow coupler would reduce that 90psi. A fire extingusher sized accumulator at the booth will help reduce that 90psi also. You need volume at the gun more than you need psi. When flow is restricted through 50' of 3/8" hose or longer then Psi has to be upped to compensate. I've noticed that the cheap wall type regulators from devilbiss or sharp that run about 100 bucks have a lot of reduced flow. When I used mine I would have the wall regulator set at 65psi and the gun would read about that until the trigger was pulled and it would drop to 25 psi. Get a nice big regulator at beginning of the gun hose. Your going to paint fine with 90psi but everytime you pull the trigger you get a blast of unnecessary air.
 
You must log in or register to reply here.
Back
Top